I ran another level, and there's no ferno bonus. First shot, I used hardened assault and killed 3. Ferno killed off the last. Zomm never went, so the turn never ended. Next floor, no bonus from ferno, just the one from having Agnons turn.

Edit: pictures uploaded in the wrong order, but I think you can see what I meant.

Ah, sorry, I misunderstood what you meant in your initial post. I thought you were talking about gaining energy normally, I didn't realize you meant from Updraft. Each floor is considered a separate "dungeon", and updraft only counts the end of rounds and rooms, so Updraft will not count energy at the end of a floor.